As teh onlky person who describes themselve as a Petroleum Engineer to post on this board, can I point out a few facts that are often ignored when discussing published reserves?
The 1100 billion barrels of reserves quoted in the EIA website and in the BP Statisitcal Energy Review are PROVED reserves, ie those reserves which current engineering and geological understanding indicates can be recovered under existing economic and operating conditions.
So there is an explicit influence of the price of oil- if the oil price goes up, the amount of proved reserves also goes up, without any exploration effort at all! Proved reserves have increased year on year every year apart from a couple of wobbles in 1990 after the price crash at the end of the '80s and again in 1997 when the oil price dropped to $10/bbl (god 1997 was awful!)
Then there are the other types of reserves: Probable and Possible....the USGS suggests there is at least another half a billion barrels to be discovered (ie the average of the sum of the probable and possible around the world). Then you add in the non conventional oil sources: heavy oil, tar sands, oil shales, marine gas hydrates, coal bed methane etc.
There have been large discoveries regularly (large is generally accepted as over a billion barrels): Girassol, Shakhalin, AGT, Chriag, even a mature province like the North Sea threw up Buzzard a couple of years ago, and Chevron are rumoured to have found something very big West of Shetland. Ture, there haven't been many discoveries like Ghawar in Saudi Arabia, or Cantarell in Mexico, but these super giant fields are the exception rather than the rule- there's only a handful of them anyway!
Finally the Hubbert Peak only works once you've gone past the peak- it can't predict where the peak will be....and it only works within a closed system; change the sytem and the peak changes: how come oil prodution from the US lower 48 is increasing compared to a decade ago, when the Hubbert's peak for lower 48 production shows that it peaked in the 70's and should be on a steady, unstoppable decline? Answer: there's a new province, the deep and ultra deep Gulf of Mexico.
Hydrocarbons will be important as a source of energy at least until I retire, and proabaly at least until my children retire too.